FMS flight management systems are well known. They make it possible to formulate the flight plan of an aircraft on each mission, by taking account of parameters specific to the aircraft and to the flight conditions such as the payload, the weight of the aircraft, the quantity of fuel on board, the temperature, the wind as well as time constraints imposed by the ATC air traffic control bodies: required departure and/or arrival time slot.
The flight plan describes notably the set of points (“waypoints”) or positions above which the aircraft must pass, with notably the corresponding altitude and speed at each point. It provides a vertical flight profile for the various phases of the aircraft, typically the climb phase CLB, the cruising phase CRZ and the descent phase DES.
Several types of flight plan are considered by FMS systems. The pilot usually has at his disposal an active flight plan, a temporary flight plan and one or more secondary flight plan(s).
The active flight plan is the flight plan currently undergoing processing and the latter controls the aircraft's automatic pilot.
The temporary flight plan is a copy of the active flight plan to which modifications are made by the pilot, such as for example point or turning point addition or modification. This flight plan can thereafter become the active flight plan when the pilot so decides.
The secondary flight plan is a stored flight plan that may be selected as active flight plan by decision of the pilot.
In the current realizations, the information relating to these various flight plans is displayed in the aircraft flight deck by using two screens. A first screen, usually called the horizontal navigation screen, and designated by the acronym ND standing for the expression “Navigation Display”, makes it possible to graphically display the active, temporary, and/or secondary flight plans, projected horizontally on the terrestrial surface with the names (“ident”) of the points of the flight plan. A second screen, called the control and display unit, or else Pilot FM interface, and usually designated by the acronym CDU standing for the expression “Control Display Unit”, serves as interface for displaying and editing each flight plan, comprising notably the list of points of the flight plan with their predictions of time, altitude, speed, fuel and wind and with the parameters between the points (name of route or procedure, distance, angle of route, etc.). The pilot can, with the aid of this interface, make modifications to each of the flight plans.
These screens are distinct and therefore display information in two different places. For example, the horizontal navigation screen ND can be in the head-level position whereas the control and display unit can be in the head-down position. When the pilot makes modifications to the temporary flight plan, it is then difficult to follow on two different screens the alterations in the trajectory and predictions associated with the points of the trajectory and therefore to be able to easily compare the active reference flight plan and the temporary flight plan.